This invention relates generally to location systems. More particularly, the invention provides a system and method for monitoring the location of members of a group relative to each other and relative to a perimeter for ingress or egress.
It is every parent's worst nightmare to have an outing with the children for shopping or recreational purposes and to turn around and suddenly find that a child is no longer within a line of sight, whether because the view to the child is obstructed or because the child has left the location of the parents. It is equally frustrating to become separated from a group or to have a group member unaccounted for. Endless hours are spent fretting and searching because a group member is missing or because a group member was left behind.
Location technologies have been developed to assist in the location of individuals as well as objects. Global Positioning Systems, which are funded and controlled by the U.S. Department Of Defense, have found many thousands of civilian users all over the world. Global Positioning Systems (GPS) provides specially coded satellite signals that can be processed in a GPS receiver enabling the receiver to compute position, velocity, and time. GPS is used by civilians without charge or restrictions. The actual position of a GPS receiver can be determined quite accurately. GPS systems have found their way into automobiles, military vehicles, civilian defense and all manner of other vehicles. For example, hikers use portable GPS systems. Personal digital assistance (PDAs) and other devices increasingly incorporate GPS capabilities. A European funded satellite system called “Galileo” will be available in the near future and will offer even more accurate location capabilities.
Other technologies utilize network topology and transmission parameters to identify a position of a transmitting device. In one such system, the mobile network base station cell area is used as the location of the mobile handset. The positioning accuracy achieved depends upon the network cell size, which, if outside of urban areas, can be large. Another system determines the mobile handset position by measuring the time of arrival of a handset signal to at least three network base stations, which must be synchronized. In yet another system, time measurements are made at special receiving locations to improve overall positioning accuracy.
Cell phones usage is rising dramatically within the United States and throughout the world. It is even the case that many people are abandoning their landlines in favor of an all-digital wireless communication existence. With many people carrying cell phones both on their persons as well as on their vehicles, it was reasoned that one could determine the position of a cell phone at any point in time provided that the cell phone was turned on. Since this is the vast majority of time, an opportunity existed for emergency response personnel to locate a cellular phone user in the event of an emergency.
As a consequence of this, the E911 standard was mandated by the government to allow 911 providers to know where a cellular customer is when a call originates from a cell phone. Broadly speaking, there are two basic types of solutions—network-based solutions and handset-based solutions. In the case of network-based solutions, receivers at known locations (i.e., at base stations) measure the direction or, more typically, the time of arrival of the signal emitted by the mobile unit. In the case of the latter, having a timing reference and knowing the speed that the radio signal travels is a constant (i.e., the speed of light), it is possible to estimate the range of the mobile unit from the base station. With three base stations at known locations making the measurements, it is possible to unambiguously estimate the location of the mobile unit. There are many refinements to this basic triangulation technique including using combinations of angle-of-arrival (direction) and field strength, for example. Systems like this are referred to as network-based solutions for the rather obvious reason that the measurements and calculations are done in the network.
In a handset-based solution, the situation is reversed with the handset making the measurements and the calculations. In one approach, the handset measures the time of arrival of signals transmitted from Global Positioning System (“GPS”) satellites and uses a similar triangulation techniques to calculate its position. In the most commonly used approach, some of required processing is actually carried out in the network to improve the performance of the system. Likewise, another commonly used approach, known as Enhanced Observed Time Difference of Arrival (“E-OTD”), is regarded as a hybrid system because the required measurements are distributed between the handset and the network.
In fact, it is anticipated that some GPS applications will be available for cell phones shortly. However, these applications are limited to telling a cell phone user where that user is located or conveying that GPS information to some emergency response vehicle.
While such applications are useful, there is also a tremendous amount of utility to having that location information available directly to other types of users. U.S. Pat. No. 6,362,778 issued to Neher for “A Personal Location Detection System,” describes a system and method for transmitting a location request signal to a central station and, in response to the request, providing location information to one or more person on a contact list. While this information is useful, it is limited to providing location information in a reactive mode of a single device.
U.S. Pat. No. 6,100,806 issued to Gaukel for a “Apparatus And Method For Continuous Electronic Monitoring And Tracking Of Individuals,” describes an apparatus and method of monitoring mobile objects or persons utilizes the Global Positioning System satellites and cellular telephone communications. Remote units are worn on the monitored person or object. These remote units would comprise a position and data sensors as well as the transmitter device to transmit the information back to a central tracking station. These data for processing and displaying the information. Rules of compliance are described in the context of a house arrest application. The rules allow a very broad range of tracking conditions, involving time, location, observation, and confirmation. Typical rules of compliance for light enforcement restrict the “prisoner” to the house during non-working hours, to allow travel to and from work, and limited travel with prearranged call-in for permission (hereinafter “inclusion” zones). Under these conditions, the central control tracking station defines the house on the computer in terms of a set of coordinates with a certain boundary. Likewise, a route to and from work is defined on the computer as a path with a certain width. In some cases, very loose travel rules may apply, with the limitation being on not allowing the prisoner to visit certain businesses, such as bars or other undesirable locations (hereinafter “exclusion” zones). These locations can be programmed in, monitored, and reported on. The variations are limited only by the ability of law enforcement to devise workable rules of compliance which make reasonable use of resources, are effective, and are agreeable to the courts.
While monitoring the location of an individual is useful, it would be beneficial to the capability to monitor the location of group members relative to each other and to one or more defined boundaries and to relate this information to some or all of the members of the group. The members of a group would comprise an ad hoc network. The location of each device within the ad hoc network would be constantly monitored in relationship to other devices that are members of the ad hoc network. Additionally, the location of each member device would be monitored in relationship to a defined perimeter. Such a system would permit an egress perimeter to be defined, in which member devices are permitted to roam but not leave, and permit an ingress perimeter to be defined, in which member devices are not permitted to enter. The system would provide a graphical display of the proximity of the members of the network to the perimeter boundary and warnings when a boundary is approached or crossed.